Methods of patterning a conductor on a substrate

ABSTRACT

A method of patterning a conductor on a substrate includes providing an inked elastomeric stamp inked with self-assembled monolayer-forming molecules and having a relief pattern with raised features. Then the raised features of the inked stamp contact a metal-coated visible light transparent substrate. Then the metal is etched to form an electrically conductive micropattern corresponding to the raised features of the inked stamp on the visible light transparent substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication 61/032,273 filed on Feb. 28, 2008, which is herebyincorporated by reference in its entirety.

BACKGROUND

There are numerous methods for patterning metals on surfaces, many ofwhich are widely practiced commercially, including for examplephotolithography with etching or with plating, inkjet printing,screen-printing, and laser patterning. At the same time, there are manyother unique methods that to date have failed to displace the incumbentprocesses commercially, for example due to lack of a true advantage ordue to significant technical barriers to implementation. Significanttechnical barriers have impeded the commercialization of microcontactprinting in the etch-patterning of metals.

Microcontact printing is the stamping or rotary printing ofself-assembled monolayer (SAM) patterns on substrate surfaces. Theapproach exhibits several technologically important features, includingthe ability to be carried out for very fine scale patterns (e.g.,feature size of one tenth of a micrometer) and with the extension of thepatterned monolayer to the patterning of metals, ceramics, and polymers.Notwithstanding these features, the method has been revealed throughextensive research to pose significant challenges related to patterngeometry flexibility and to scale-up. By pattern geometry flexibility,what is meant is the ability to apply a method of patterning to a widerange of pattern geometries. For example, in the art it is known thatmicrocontact printing patterns with widely spaced features leads tostamp deformation, including roof collapse, which leads to unacceptablepattern distortion and artifacts.

These issues have led to the engineering of composite stamps withcomplicated constructions, usually comprising very stiff or very thinlayers of the elastomer stamp material, or sometimes including mountingof the stamp on supports or backplanes with specified properties. Inother approaches, stamps with significant relief have been proposed,leading to challenges in mastering and printing. Often, the materialchanges or stamp construction or support measures lead to challenges ingenerating an inked stamp that can be used to print patternsefficiently, for example with high throughput and at competitive cost.Thus, in order to avoid the negative ramifications and complications ofextensive stamp material substitutions or multilayer stamp construction,there is a need in the art to define pattern geometries that are morecompatible with standard stamp materials and low levels of stamp relief.

As another example, in the art it is known that kinetic aspects of theprocess can substantially constrain the range of SAM pattern geometriesthat can be microcontact printed effectively and efficiently. Thekinetic phenomena that govern successful microcontact printing of SAM'sinclude, for example, bulk diffusion of SAM-forming molecules in thestamp, surface diffusion of the same along the stamp, surface diffusionof the same along the substrate, surface diffusion of the same along theSAM itself, interfacial transport of the same at the stamp-substrateinterface, and reaction kinetics for the SAM-forming molecule with thesubstrate surface. The convolution of these kinetic factors makes theability, let alone the sufficient optimization for commercialization, ofmicrocontact printing to generate any particular pattern uncertain.

Another important challenge in microcontact printing relates to printingfeatures of different scale simultaneously. Owing to the aforementioned(but not entirely understood) kinetic factors, it is unknown whetherparticular combinations of features sizes and spacings can be printedeffectively and with useful speeds. No obvious and practical conditionexists for printing alkanethiols to form both small and large featuresat the same time while maintaining the accuracy of the former.

Another important but unpredictable factor that influences whether aparticular metal pattern can be successfully generated under a given setof printing and etching conditions is the surface onto which the SAM isprinted, for example as determined by a substrate onto which the metalis deposited. Factors such as surface roughness and readily achievablecleanliness can vary substantially from one substrate type to the next(for example, polymer films as opposed to semiconductor wafers) and thusimpacts the ability or conditions under which a metal pattern can begenerated thereon.

Thus, there is a need in the art for combinations of pattern geometriesand microcontact printing conditions, including ink formulation andstamp inking procedures, that allow for the effective and efficientetch-patterning of metal micropatterns, on commercially viablesubstrates for various applications.

BRIEF SUMMARY

The present disclosure relates to methods of patterning conductors on asubstrate.

In a first embodiment, a. method of patterning a conductor on asubstrate includes providing an inked elastomeric stamp inked withself-assembled monolayer-forming molecules and having a relief patternwith raised features. The relief pattern having a low density regionmeasuring at least 5 square millimeters (mm²). The low density regionincludes an average area density value of raised features between 0.5 to10%, linear segments having a width value between 0.5 to 25 micrometers(μm), and a distance value between adjacent raised features of less than1 mm. Then the raised features of the inked stamp contact a metal-coatedvisible light transparent substrate. Then the metal is etched to form anelectrically conductive micropattern corresponding to the raisedfeatures of the inked stamp on the visible light transparent substrate.

In another embodiment, a method of patterning a conductor on a substrateincludes providing a metal-coated visible light transparent substratehaving a relief pattern with raised features, the relief pattern havinga low density region measuring at least 5 mm². The low density regionincludes an average area density value of raised features between 0.5 to10%, linear segments having a width value between 0.5 to 25 μm, and adistance value between adjacent raised features of less than 1 mm. Thenan inked elastomeric stamp inked with self-assembled monolayer-formingmolecules contacts the metal-coated visible light transparent substrate.As used herein “contacts” encompasses direct contact as well as a smallseparation such as an ink thickness. Then the metal is etched to form anelectrically conductive micropattern on the visible light transparentsubstrate raised features.

In a further embodiment, a method of patterning conductors on asubstrate includes providing an inked stamp with a relief pattern withraised features. The inked stamp includes linear organosulfurself-assembled monolayer-forming molecules with chain length from 16 to18 atoms at a concentration within the stamp of 1 to 10 millimolar (MM).The relief pattern has a low density region measuring at least 5 mm².The low density region includes an average area density value of raisedfeatures between 0.5 to 5%, linear segments having a width value fromapproximately 1 to 4 μm, and a distance value between adjacent linearsegments of less than 500 μm. The relief pattern further includes araised feature measuring at least 25 μm in width. Then the inked stampcontacts a metal-coated visible light transparent substrate for acontact time in a range from 0.5 to 10 seconds, thereby depositing apattern of self-assembled monolayer. Then the metal is etched to form atransparent electrically conductive micropattern corresponding to theraised features of the inked stamp on the visible light transparentsubstrate. Various embodiments of the present invention are useful inapplications such as touch screen sensors for displays, electromagneticinterference (EMI) shielding films, and transparent electrodes forelectroluminescent, electrochromic or photovoltaic devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 illustrates a low density electrically conductive micropattern,the low density pattern includes 3 μm wide traces on a pitch of 200 μmin each of two orthogonal directions, leading to a fill factor fortraces of approximately 3%;

FIG. 2 illustrates a low density electrically conductive micropattern,the low density pattern includes 3 μm wide traces on a pitch of 200 μmin each of two orthogonal directions, with breaks as shown that measureapproximately 10 μm, leading to a fill factor for traces ofapproximately 3%;

FIG. 3 illustrates a low density electrically conductive micropattern,the low density pattern measuring approximately 1.2 mm by 1.2 mm andincludes 40 isolated segments of conductor measuring approximately 225μm in length and approximately 3 μm in width, leading to a fill factorfor traces of approximately 2%;

FIG. 4 illustrates a low density electrically conductive micropattern,the low density pattern includes 3 μm wide traces and apex to apex widthfor the hexagonal cells of approximately 175 μm, leading to a fillfactor for traces of approximately 3%;

FIG. 5 illustrates an electrically conductive pattern comprising a lowdensity micropattern region, the low density micropattern regionincludes 3 μm wide traces on a pitch of 200 μm in each of two orthogonaldirections, leading to a fill factor for traces of approximately 3%, anda larger feature in the form of a continuous metal region measuring 1.2mm by 1.2 mm;

FIG. 6 illustrates a low density relief pattern for a stamp, the solidlines corresponding to linear raised features on the stamp surface andthe dotted line outlining the region. The low density micropatternincludes 3 μm wide raised linear features on a pitch of 700 μm, leadingto fill factor for raised features of approximately 1%;

FIG. 7 illustrates a low density relief pattern for a stamp, the solidlines corresponding to linear raised features on the stamp surface andthe dotted line outlining the region. The low density micropatternincludes 3 μm wide raised linear features on a pitch of 700 μm, withbreaks as shown that measure approximately 10 μm, leading to fill factorfor raised features of approximately 1%;

FIG. 8 is a scanning electron photomicrograph showing an electricallyconductive pattern including a low density micropattern region with 3 μmwide conductive metal traces in the form of a square mesh with pitch ofapproximately 200 μm, leading to a 3% fill factor, together with a 2 mmby 2 mm region of continuous metal;

FIG. 9 is a scanning electron photomicrograph showing an electricallyconductive pattern including a low density micropattern region with 5 μmwide conductive metal traces in the form of a square mesh with a 5% fillfactor;

FIG. 10 is a scanning electron photomicrograph showing an electricallyconductive pattern including a low density micropattern region with 3 μmwide conductive metal traces in the form of a hexagonal mesh with apexto apex width of approximately 175 μm, leading to a 3% fill factor;

FIG. 11 is a scanning electron photomicrograph showing a small portionof an electrically conductive pattern including a low densitymicropattern region with approximately 5 μm wide conductive metal tracesin the form of a hexagonal mesh with apex to apex width of approximately175 μm, leading to a 5% fill factor (the image includes fine lines drawnacross the three conductive line segments for the purpose of guiding theeye with respect to the width of the line segments);

FIG. 12 is a scanning electron photomicrograph showing a small portionof an electrically conductive pattern including a low densitymicropattern region with 3 μm wide conductive metal traces in the formof a hexagonal mesh with apex to apex width of approximately 175 μm,leading to a 3% fill factor (the image includes fine lines drawn acrossthe three conductive line segments for the purpose of guiding the eyewith respect to the width of the line segments);

FIG. 13 illustrates a schematic diagram of a touch screen sensor;

FIG. 14 illustrates a perspective view of a conductive visible lighttransparent region lying within a touch screen sensing area.

FIGS. 15, 15 a and 15 b illustrate various portions of a first patternedsubstrate;

FIGS. 16, 16 a, and 16 b illustrate various portions of a secondpatterned substrate;

FIG. 17 illustrates a projected capacitive touch screen transparentsensor element constructed from the first and second patternedsubstrates of FIGS. 15 and 16.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part hereof and in which are shown by way ofillustration several specific embodiments. It is to be understood thatother embodiments are contemplated and may be made without departingfrom the scope or spirit of the present invention. The followingdetailed description, therefore, is not to be taken in a limiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The use of numerical ranges by endpoints includes all numbers withinthat range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5)and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the context clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the context clearlydictates otherwise.

As used herein, “visible light transparent” refers to the level oftransmission being at least 80% transmissive to at least onepolarization state of visible light, where the % transmission isnormalized to the intensity of the incident, optionally polarized light.It is within the meaning of visible light transparent for an articlethat transmits at least 60% of incident light to include microscopicfeatures (e.g., dots, squares, or lines with minimum dimension, forexample width, between 0.5 and 10 μm, or between 1 and 5 μm) that blocklight locally to less than 60% transmission (e.g., 0%); however, in suchcases, for an approximately equiaxed area including the microscopicfeature and measuring 1000 times the minimum dimension of themicroscopic feature in width, the average transmittance is greater than60%.

A polymeric “film” substrate is a polymer material in the form of a flatsheet that is sufficiently flexible and strong to be processed in aroll-to-roll fashion. By roll-to-roll, what is meant is a process wherematerial is wound onto or unwound from a support, as well as furtherprocessed in some way. Examples of further processes include coating,slitting, blanking, and exposing to radiation, or the like. Polymericfilms can be manufactured in a variety of thickness, ranging in generalfrom about 5 μm to 1000 μm. In many embodiments, polymeric filmthicknesses range from about 25 μm to about 500 μm, or from about 50 μmto about 250 μm, or from about 75 μm to about 200 μm. For films thatinclude a relief structure on one or both major surfaces, what is meantby thickness of the film is the average thickness across the area of thefilm.

A “self-assembled monolayer” generally refers to a layer of moleculesthat are attached (e.g., by a chemical bond) to a surface and that haveadopted a preferred orientation with respect to that surface and evenwith respect to each other. Self-assembled monolayers have been shown tocover surfaces so completely that the properties of that surface arechanged. For example, application of a self-assembled monolayer canresult in a surface energy reduction and allow selective etching ofmetal that is not coated with the self-assembled monolayer.

The present disclosure relates to methods of metal patterning based onmicrocontact printing and etching. As used herein, “metal” and“metalized” refers to a conductive material such as an elemental metalor alloy which is suitably conductive for the intended purpose. Theimprovements include preferred pattern geometries, and their combinationwith preferred inking and printing parameters. The pattern geometries,inking parameters, and printing parameters combine to define preferredoperating windows for metal patterning, especially on polymer films. Afirst operating window has the advantage of efficiently and reproduciblygenerating patterns of metals with very low fill-factor comprising finetraces using standard stamp materials and easily achievable andmanageable stamp relief. A second operating window has the advantage ofefficiently and reproducibly generating patterns of metals with a firstregion having a very low fill-factor comprising fine traces and a secondregion being a larger feature (i.e., larger than the fine traces) usingof standard stamp materials and easily achievable and manageable stamprelief. The windows also include printing times that are preferred forcost-effective use of equipment, but also practicality ofimplementation. While the present invention is not so limited, anappreciation of various aspects of the invention will be gained througha discussion of the examples provided below.

The ability to pattern conductive materials effectively, efficiently andreproducibly using microcontact printing and etching depends on thegeometry of the pattern of raised features, due to a number ofcomplicating factors. The complicating factors include the effects ofthe pattern of stamp raised features on i) the local pressure applied tothe substrate in the contact areas of the stamp or plate, as defined bythe raised features, ii) stamp collapse in areas of the relief patternbetween the raised features, iii) buckling of the raised features, andiv) the effective amount of SAM-forming molecules within the stamp orplate materials, near to the different raised features.

These effects impact the quality of the microcontact printed pattern, interms of i) desirably avoiding pinholes in the intended conductorregions after patterning, ii) desirably avoiding distortion of conductorregions due to stamp or plate feature buckling, and iii) desirablyavoiding extraneous conductor deposits resulting from collapse of thestamp or plate in regions between intended conductor regions. Theunderlying phenomena and mechanisms that govern these effects of reliefpattern geometry on the ability to pattern conductive materialseffectively are complex and in some cases at odds with each other.

The application of greater force between the stamp or plate and thesubstrates, leading to greater local pressure in the regions of contactbetween the two, has been found to be helpful in general fortransferring a monolayer of molecules that form the self-assembledmonolayer that allows for etch-patterning of conductor regions without ahigh density of pinholes, but can lead to collapse of the stamp inregions between the raised features of the relief pattern. As anotherexample, spacing of raised features close together has been found to behelpful for avoiding collapse of the stamp and the generation ofunintended conductor regions between the raised features of the reliefpattern, but as the features are made to be closer together, an apparentnegative effect of pattern density on the availability of sufficientSAM-forming molecules from the stamp or plate leads to the printing of aSAM mask that is unable to give conductor regions after etching that aresubstantially free of pinholes. The same concern regarding havingsufficient concentration of SAM-forming molecules to protect features inhigh density patterns also applies to the need to protect large featureswith printed SAM's during etching. And, importantly, at odds with thedesire to have sufficient concentration of SAM-forming molecules in thestamp and sufficient stamping times to allow adequate SAM formationwithin the large feature regions is a negative effect that suchparameters can have on feature size accuracy for smaller features. To besure, there is a complex interplay between many factors in themicrocontact print-patterning of conductors. Importantly, the effectslisted and elaborated upon above become substantially more challengingto manage as one attempts to apply the method described above formicrocontact printing and etching at higher and higher speed needed forcommercial viability. Notwithstanding this complexity, it has beendiscovered that certain desirable conductor pattern geometries, asderived from stamp or printing plate relief pattern geometries, can befabricated by microcontact printing and etching at attractive speeds.

We have discovered that certain two-dimensional pattern geometries forthe raised features of microcontact printing stamps allow for theeffective, efficient, and reproducible generation of etched metalpatterns when the stamps are used to print SAM-based etch masks. Thepattern geometries under the current invention may take an essentiallyinfinite number of different forms, but they all are consistent withcertain descriptions, as given below.

All of the patterns include a low density region. By low density, whatis meant is that the area fraction of raised features for the stamp orthe area fraction of metal remaining after pattern-wise etching from thesubstrate is low, as given below. The term low density refers to thepattern density, which is used interchangeably herein with fill factoror fill-factor. Low-density is used interchangeably with low density.The low density region in the pattern is at least 5 mm² in area,preferably at least 10 mm². In some embodiments the low density regionis greater than 1 square centimeter (cm²) in area, greater than 10 cm²in area, greater than 50 cm² in area, or even greater than 100 cm² inarea.

In some embodiments, the pattern includes the low density region with norequirement for the presence or absence of any other types of regions.In other embodiments, the pattern includes the low density regiontogether with a region that includes a larger pattern feature (e.g., awide trace or contact pad, measuring at least 10 μm, preferably at least25 μm in width, for example 100 to 1000 μm in width). As a furtherexample of the latter, the pattern of raised features on the stamp(which defines the metal pattern after etching) may include largerraised features that are the same size as allowed for an entire lowdensity region, for example, 5 mm² or larger. Such a raised featurewould define a region in itself with a density or fill factor of 1,which is not low. The pattern of the stamp, and hence the metal afterpattern-wise etching, is comprised of raised features that define atwo-dimensional relief pattern. All points in the relief pattern that donot lie within a raised feature are described herein to be “non-raisedpoints” in the relief pattern.

Geometries in low-density regions preferably include raised features inthe form of non-parallel linear elements. By including non-parallellinear elements, what is meant is that the pattern includes linearelements where not all of the linear elements are parallel with eachother. It has been found that geometries comprising non-parallel linearelements significantly increase the ease with which one can generatemetal patterns having surprisingly low fill factor, for example less10%, or less than 5%, or less than 4%, or less than 3%, or less than 2%,or less than 1%, or even lower, for example 0.5%. Although these fillfactor values for patterns, or regions of patterns, are preferred, it iswithin the scope of the disclosure for the patterns to have fill factorgreater than 5%, greater than 10%, or even greater than 15%. In someembodiments the fill factor within a low density region is between 0.5and 20%, in some embodiments between 0.5 and 15%, in some embodimentsbetween 0.5 and 10%, in some embodiments between 0.5 and 5%, in someembodiments between 0.5 and 4%, and in some embodiments between 1 and3%.

The pattern of raised features for the stamp, and in turn the pattern ofconductor elements after etching, in the low density region is alsodescribable in terms of a distance value between adjacent features andadjacent elements. It is preferred that the distance value between alladjacent raised features of the stamp in the low density region be lessthan or equal to approximately 1 mm. It is more preferable in someembodiments that the distance value between all adjacent raised featuresbe less than or equal to approximately 500 μm. However, it is within thescope of this disclosure for the distance value between adjacentfeatures and adjacent elements to be greater than 1 mm, for examplebetween 1 mm and 2 mm or between 1 mm and 5 mm. To determine thedistance values between adjacent raised features in a low densityregion, one first identifies the adjacent raised features. Adjacentraised features are identified differently for a low density regioncomprising a two-dimensional mesh of raised linear features versus a lowdensity region comprising isolated raised features. Considering firstthe case of a two-dimensional mesh of raised features (for exampleraised features that define a square mesh, a hexagonal mesh, or otherpolygonal mesh), adjacent raised features are defined with reference tothe mesh cell that they define. For different mesh cell shapes,identification of adjacent raised features requires different rules.First, for a mesh cell in which the centroid of the open area of thecell lies within the open area (i.e., the cell has an interiorcentroid), the adjacent raised features for that cell are the raisedfeatures that intersect the shortest possible straight line that can bedrawn through the centroid and that extends to two boundaries of thecell; and, the distance value between adjacent raised features for thatcell is the length of the straight line. In the case just described,raised features other than those contacted by the straight line are notconsidered adjacent. Second, for a mesh cell in which the centroid ofthe open area of the cell lies outside the open area (i.e., the cell hasan exterior centroid), the adjacent raised features for that cell aredefined first by partitioning the cell area into the minimum number ofsub-cell areas required for the sub-cell areas each to have their owncentroid within their sub-cell area (i.e., each sub-cell area has aninterior centroid). Then, for such a mesh cell, there are multiple pairsof adjacent raised features, with one pair corresponding to eachsub-cell area. For each sub-cell area, the adjacent raised features forthat sub-cell area are the raised features that intersect the shortestpossible straight line that can be drawn through the centroid for thatsub-cell area and that extends to two boundaries of the sub-cell area;and, the distance value between adjacent raised features for thatsub-cell area is the length of the straight line. For low densityregions comprising isolated raised features, adjacent raised featuresare more directly understood by those of ordinary skill in the art. Theyare pairs of raised features for which there is no other raised featurein the space between them. It has been discovered that preferred stamprelief pattern geometries for the low density region include raisedfeatures that define a two-dimensional mesh with cells having interiorcentroids and with the adjacent raised features for cells having adistance value between them that is less than or equal to approximately1 mm, or less than or equal to approximately 500 μm.

It is preferred that the fill-factor of the relief pattern is uniform inthe low-density region. To be more specific, in the low-density region,it is preferred that the density of raised features, expressed as thearea fraction occupied by raised features in any portion of the region,not vary by more than a certain variability factor, expressed aspercentage of the average density in the entire low-density region.Relevant sizes for the area portion include 1 mm², 2 mm², 5 mm², and 10mm². In many embodiments, the variability factor is less than 75%, orless than 50%, or less than 25%, or less than 10%, or less than 5%, oreven lower.

FIG. 1 through FIG. 5 provide a non-limiting set of useful electricallyconductive micropatterns. FIG. 1 illustrates a low density electricallyconductive micropattern, the low density pattern includes 3 μm widetraces on a pitch of 200 μm in each of two orthogonal directions,leading to a fill factor for traces of approximately 3%. FIG. 2illustrates a low density electrically conductive micropattern, the lowdensity pattern includes 3 μm wide traces on a pitch of 200 μm in eachof two orthogonal directions, with breaks as shown that measureapproximately 10 μm, leading to a fill factor for traces ofapproximately 3%. FIG. 3 illustrates a low density electricallyconductive micropattern, the low density pattern measuring approximately1.2 mm by 1.2 mm and includes 40 isolated segments of conductormeasuring approximately 225 μm in length and approximately 3 μm inwidth, leading to a fill factor for traces of approximately 2%. FIG. 4illustrates a low density electrically conductive micropattern, the lowdensity pattern includes 3 μm wide traces and apex to apex width for thehexagonal cells of approximately 175 μm, leading to a fill factor fortraces of approximately 3%. FIG. 5 illustrates an electricallyconductive pattern comprising a low density micropattern region, the lowdensity micropattern region includes 3 μm wide traces on a pitch of 200μm in each of two orthogonal directions, leading to a fill factor fortraces of approximately 3%, and a larger feature in the form of acontinuous metal region measuring 1.2 mm by 1.2 mm.

With regard to the non-parallel linear elements, it has been found thatpreferred low density pattern geometries are characterized by having aplurality of the linear elements and no non-raised points more than acertain distance from a linear element for all directions (within plusor minus 10 degrees) around that point (herein called the “maximumseparation distance” from a linear element). The limitation of plus orminus 10 degrees from a given direction acknowledges that it is withinthe scope of the disclosure for there to be minor openings betweenlinear elements. Linear elements with minor openings are particularlyuseful in a low density region for supporting the stamp in portions ofthe region between contiguous elements, for example between meshes.

FIG. 6 illustrates a low density relief pattern region 100 for a stamp,the solid lines 110 corresponding to linear raised features on the stampsurface and the dotted line outlining the region. The low densitymicropattern comprises 3 μm wide raised linear features 110 on a pitchof 700 μm, leading to fill factor for raised features of approximately1%. A non-raised point 120 is positioned in the space between raisedfeatures. A vector measuring 1 mm in magnitude 130, together withsatellite vectors 140 and 150, and the area 160 which is bounded by thedashed line, can be swept through all angles (360 degrees) and observedto overlap with a raised linear element for all angles. Under suchcircumstances, the non-raised point is said to have a maximum separationdistance from a raised linear feature of less than 1 mm for alldirections.

FIG. 7 illustrates a low density relief pattern region 200 for a stamp,the solid lines 210 corresponding to linear raised features on the stampsurface and the dotted line outlining the region. The low densitymicropattern comprises 3 μm wide raised linear features 210 on a pitchof 700 μm, with breaks as shown that measure approximately 10 μm,leading to fill factor for raised features of approximately 1%. Anon-raised point 220 is positioned in the space between raised features.A vector measuring 1 mm in magnitude 230, together with satellitevectors 240 and 250, and the area 260 which is bounded by the dashedline, can be swept through all angles (360 degrees) and observed tooverlap with a raised linear element for all angles. Under suchcircumstances, the non-raised point is said to have a maximum separationdistance from a raised linear feature of less than 1 mm for alldirections.

Preferably, the maximum separation distance for all non-raised points toa linear elements, as described above is less than 1 mm, or less than750 μm, or less than 500 μm, or less than 400 μm, or less than 300 μm,or less than 100 μm, or less than 50 μm, or even less. The linearelements have a long axis or arc length that is at least 3 times greaterthan their width, or more than 5, or greater than 10. In regions whereelectrical continuity is not required for the conductor elements thatare derived from the raised features of the stamp, it will be understoodby one of ordinary skill in the art that the benefit to printing thathas been discovered for the specified placement and shape of linearelements could be met by the placement of very closely spaced moreequiaxed elements, forming in essence a linear arrangement of tightlyspaced elements. In the case of the latter, the linear arrangement oftightly spaced elements is considered a linear conductor element. Thelinear elements may be isolated from each other, but in some embodimentsit is preferred that they are joined to create a network or mesh, forexample a square mesh or a hexagonal mesh or other polygonal mesh. Inmany embodiments, the linear elements have a width less than or equal toapproximately 25 μm, or less than or equal to approximately 10 μm, orless than or equal to approximately 5 μm, or less than or equal toapproximately 2 μm. In some embodiments the linear elements have a widthbetween 0.5 and 25 μm, in some embodiments between 0.5 and 10 μm, insome embodiments between 1 and 10 μm, in some embodiments between 1 and5 μm, in some embodiments between 1 and 4 μm, in some embodimentsbetween 1 and 3 μm, and in some embodiments between 2 and 3 μm.

For certain applications wherein a low fill-factor pattern of metal isdesired, particularly on a polymer film substrate, it has been foundthat a stamp pattern comprising a two dimensional mesh of raised linearelements having width between 1 and 10 μm and no non-raised points witha maximum separation distance from a linear element of greater than 1 mmare advantageous for generating metal patterns with a fill-factor ofbetween 0.5% and 5%, for example 2% or 3%. It has further been foundthat a stamp relief pattern comprising a two dimensional mesh of raisedlinear elements having a width between 2 and 5 μm and no non-raisedpoints with a maximum separation distance from a linear element ofgreater than 750 μm are advantageous for generating metal patterns witha fill-factor of between 0.5% and 5%, for example 2% or 3%. It hasfurther been found that a stamp relief pattern comprising a twodimensional mesh of raised linear elements having a width between 1 and3 μm and no non-raised points with a maximum separation distance from alinear element of greater than 500 μm are advantageous for generatingmetal patterns with a fill-factor of between 0.5% and 5%, for example 2%or 3%.

The aforementioned stamp geometries are advantageous for managing thechallenges of stamp collapse for standard stamp materials (for example,polydimethylsiloxane (PDMS) with a modulus between 0.5 and 5 MPa, forexample PDMS sold under the product designation Sylgard 184 by DowCorning, Midland, Mich.), especially for magnitudes of stamp relief thatare i) convenient to generate, ii) do not present challenges of bucklingfor the raised features, and iii) that do not lead to long diffusionpaths for ink molecules within the bulk of the stamp to reach printingsurface.

For the aforementioned two dimensional pattern geometries, particularlyconvenient and useful magnitudes of stamp pattern relief lie between 0.5and 10 μm, or between 0.75 and 5 μm, or between 1 and 2 μm. It ispreferred to be able to use the aforementioned standard stamp materials,as opposed to other such materials for avoiding stamp collapse such ashigher-modulus PDMS, because the standard materials provide relativeadvantages related to process throughput that relate to theiradvantageous transport properties and conformability of contact tonon-smooth surfaces, for example metalized surfaces of substrates suchas polymer films (as opposed to very smooth semiconductor wafers).

In some embodiments, in addition to the low density region describedabove, the two dimensional pattern of the stamp, and thus the finishedconductor pattern on the substrate, includes a larger feature. Thelarger feature has a minimum dimension of at least 25 μm. Examples oflarger features include lines with width (minimum dimension) of at least25 μm and square pads with edge length (minimum dimension) of at least25 μm. In the case of complicated geometries, for example wherein acontiguous conductor deposit may include fine scale elements and largerscale elements, it will be understood by one of ordinary skill in theart that the attachment of a fine scale element to a larger scaleelement does not reduce the minimum dimension of the larger scaleelement, as a feature itself, to that of the fine scale element. To bemore clear, by way of an example, a contiguous conductor deposit on asubstrate that includes a square pad measuring 1 mm by 1 mm and thatalso includes fine scale traces (e.g., 1 m in width) attached to thepad, for example that form a low density mesh, is made up of a largerfeature (the pad) and the low density mesh (i.e., the attachment of the1 μm wide traces to the 1 mm by 1 mm wide pad does not cause the minimumdimension of the feature that includes the pad to be 1 m and thereforenot within the definition of a larger feature). In some embodiments, thelarger feature has a minimum dimension of at least 50 μm, in someembodiments at least 100 μm, in some embodiments at least 200 μm, insome embodiments at least 500 μm, and in some embodiments at least 1 mm.

Preferred stamp inking procedures and parameters, as well as printingparameters, have been discovered for the cost-effective generation ofmetal patterns of the aforementioned geometries by microcontact printingfollowed by etching, particularly starting with metalized polymer films.More specifically, preferred molecules and their concentration in thestamp have been uncovered for the practical, high-speed printing ofSAM-based etch masks. The molecules generate thiolate monolayers on themetal surface, and include alkylthiols, dialkyl disulfides, dialkylsulfides, alkyl xanthates, dithiophosphates, and dialkylthiocarbamates.The molecules are characterized by a tail group or groups attached to asulfur atom, wherein the tail group or groups have between 14 and 20atoms along their backbone, preferably 16, 17, or 18 atoms. The atomsalong the backbone are preferably carbon atoms. Preferably the inksolution comprises alkyl thiols such as, for example, linear alkylthiols:

HS(CH₂)_(n)X

where n is the number of methylene units and X is the end group of thealkyl chain (for example, X=—CH₃, —OH, —COOH, —NH₂, or the like).Preferably, X=—CH₃ and n=15, 16, or 17, corresponding to chain lengthsof 16, 17, or 18, respectively. Other useful chain lengths include 19and 20. For linear molecules bearing a sulfur-containing head group forattachment to a metal, the chain length is determined as the number ofatoms along the linear arrangement of bonded atoms between and includingthe atom that is bonded to the sulfur atom and final carbon atom in thelinear arrangement. It is within the scope of this disclosure for themonolayer-forming molecule to be branched, for example with side groupsattached to the linear arrangement of bonded atoms that define thechain. Useful end groups include those described, for example, in: (1)Ulman, “Formation and Structure of Self-Assembled Monolayers,” ChemicalReviews Vol. 96, pp. 1533-1554 (1996); and (2) Love et al.,“Self-Assembled Monolayers of Thiolates on Metals as a Form ofNanotechnology,” Chemical Reviews Vol. 105, pp. 1103-1169 (2005). TheSAM-forming molecules may be partially fluorinated or perfluorinated.Where particular SAM-forming molecules are called out herein as usefulor preferred, it will be understood by one skilled in the art that othermolecules which share the important printing attributes for the intendeduse with those molecules will be equivalently useful or preferred.

The SAM-forming molecules are present in the stamp, adjacent to theprinting surface, preferably within a specified range of concentration.With respect to adjacency to the printing surface of the stamp, theconcentration can be taken to be specified for the volume of the stampdefined as being within a distance of 10 μm from the stamping surface.The concentration in the stamp can be measured for example bymicrotoming a thin layer of elastomer from the printing surface of thestamp and then carrying out chemical analysis of the thin layer, forexample with or without leaching the monolayer forming molecules out ofthe thin layer first. Useful analytical methods include massspectrometry and spectroscopic methods such as nuclear magneticresonance spectroscopy or infrared spectroscopy, as are known in theart.

With reference to the above pattern geometry descriptions for patternscomprising a low density region, generating the patterns as metalconductor deposits on substrates effectively, efficiently, andreproducibly using microcontact printing and etching has been found tobe achievable for hexadecylthiol (HDT) concentrations in the stamp,adjacent to the printing surface as described above, between 0.05 and 5mM, coupled with stamping times between 0.1 and 10 seconds. A preferredspace within this window is defined by a concentration between 0.1 and 1mM and a stamping time between 0.5 and 5 seconds. A more preferred spacewithin this window is defined by a concentration between 0.1 and 0.5 mMand a stamping time between 0.5 and 5 seconds. Outside these windows, itwas found that conductor patterns after etching were defective either inthe form of poor etching selectivity or feature broadening that renderedthe finished patterns not useful. Regarding the effectiveness,efficiency, and reproducibility of patterning, the aforementionedprocess window allows for stamping times that are short enough to becost-effective but not so short as to be overly difficult to control.The window also defines a process space that was discovered to bereproducible with respect to sufficiently consistent feature size andoverall pattern quality for rapid successive printing. Outside thiswindow, other combinations of process parameters proved inadequate forallowing repeated printing up to 10 prints. In contrast, parameterswithin the window above allowed greater than 10 rapidly successiveprints with excellent pattern quality and useful feature size accuracy.Coupled with the target stamping times, the concentration rangedescribed above was discovered to be useful for patterns comprising alow density region, for example a low density region comprising finescale features as described above. Preferably, the pressure appliedduring printing, after application of the stamp to the substrate, isbetween 0 and 10 kilopascals, with respect to the actual area of contactbetween the stamp and the substrate. The process windows described abovefor hexadecylthiol and for patterns comprising a low density region, forexample with fine features, is regarded as useful for othermonolayer-forming molecules that are 16 atoms long (not including thehead group, for example a thiol head group, not hydrogen atoms) or thatshare critical printing attributes with hexadecylthiol.

With reference to the above pattern geometry descriptions for patternscomprising a low density region, generating the patterns as metalconductor deposits on substrates effectively, efficiently, andreproducibly using microcontact printing and etching has been found tobe achievable for octadecylthiol (ODT) concentrations in the stamp,adjacent to the printing surface as described above, of between 0.05 and20 mM, coupled with stamping times between 0.1 and 10 seconds. Apreferred space within this window is defined by a concentration between0.5 and 10 mM and a stamping time between 0.5 and 5 seconds. A morepreferred space within this window is defined by a concentration between0.5 and 5 mM and a stamping time between 0.5 and 5 seconds. Outsidethese windows, it was found that conductor patterns after etching weredefective either in the form of poor etching selectivity or featurebroadening that rendered the finished patterns not useful. Regarding theeffectiveness, efficiency, and reproducibility of patterning, theaforementioned process window allows for stamping times that are shortenough to be cost-effective but not so short as to be overly difficultto control. The window also defines a process space that was discoveredto be reproducible with respect to sufficiently consistent feature sizeand overall pattern quality for rapid successive printing. Outside thiswindow, other combinations of process parameters proved inadequate forallowing repeated printing up to 10 prints. In contrast, parameterswithin the window above allowed greater than 10 rapidly successiveprints with excellent pattern quality and useful feature size accuracy.Coupled with the target stamping times, the concentration rangedescribed above was discovered to be useful for patterns comprising alow density region, for example a low density region comprising finescale features as described above. Preferably, the pressure appliedduring printing, after application of the stamp to the substrate, isbetween 0 and 10 kilopascals, with respect to the actual area of contactbetween the stamp and the substrate. The process windows described abovefor octadecylthiol and for patterns comprising a low density region, forexample with fine features, is regarded as useful for othermonolayer-forming molecules that are 18 atoms long (not including thehead group, for example a thiol head group, not hydrogen atoms) or thatshare printing attributes important for the intended use withoctadecylthiol. Octadecylthiol and like molecules are preferred tohexadecylthiol and like molecules.

With reference to the above pattern geometry descriptions for patternscomprising a low density region and a larger feature, generating thepatterns as metal conductor deposits on substrates effectively,efficiently, and reproducibly using microcontact printing and etchinghas been found to be achievable for hexadecylthiol concentrations in thestamp, adjacent to the printing surface as described above, of between0.5 and 5 mM, coupled with stamping times between 0.1 and 10 seconds. Apreferred space within this window is defined by a concentration between0.5 and 1 mM and a stamping time between 0.5 and 5 seconds. Outsidethese windows, it was found that conductor patterns after etching weredefective either in the form of poor etching selectivity or featurebroadening that rendered the finished patterns not useful. Regarding theeffectiveness, efficiency, and reproducibility of patterning, theaforementioned process window allows for stamping times that are shortenough to be cost-effective but not so short as to be overly difficultto control. The window also defines a process space that was discoveredto be reproducible with respect to sufficiently consistent feature sizeand overall pattern quality for rapid successive printing. Outside thiswindow, other combinations of process parameters proved inadequate forallowing repeated printing up to 10 prints. In contrast, parameterswithin the window above allowed greater than 10 rapidly successiveprints with excellent pattern quality and useful feature size accuracy.Coupled with the target stamping times, the concentration rangedescribed above was discovered to be useful for patterns comprising alow density region, for example a low density region comprising finescale features as described above. Preferably, the pressure appliedduring printing, after application of the stamp to the substrate, isbetween 0 and 10 kilopascals, with respect to the actual area of contactbetween the stamp and the substrate. The process windows described abovefor hexadecylthiol and for patterns comprising a low density region, forexample with fine features, is regarded as useful for othermonolayer-forming molecules that are 16 atoms long (not including thehead group, for example a thiol head group, not hydrogen atoms) or thatshare critical printing attributes with hexadecylthiol.

With reference to the above pattern geometry descriptions for patternscomprising a low density region and a larger feature, generating thepatterns as metal conductor deposits on substrates effectively,efficiently, and reproducibly using microcontact printing and etchinghas been found to be achievable for octadecylthiol concentrations in thestamp, adjacent to the printing surface as described above, of between0.5 and 20 mM, coupled with stamping times between 0.1 and 10 seconds. Apreferred space within this window is defined by a concentration between0.5 and 10 mM and a stamping time between 0.5 and 5 seconds. A morepreferred space within this window is defined by a concentration between1 and 5 mM and a stamping time between 0.5 and 5 seconds. Outside thesewindows, it was found that conductor patterns after etching weredefective either in the form of poor etching selectivity or featurebroadening that rendered the finished patterns not useful. Regarding theeffectiveness, efficiency, and reproducibility of patterning, theaforementioned process window allows for stamping times that are shortenough to be cost-effective but not so short as to be overly difficultto control. The window also defines a process space that was discoveredto be reproducible with respect to sufficiently consistent feature sizeand overall pattern quality for rapid successive printing. Outside thiswindow, other combinations of process parameters proved inadequate forallowing repeated printing up to 10 prints. In contrast, parameterswithin the window above allowed greater than 10 rapidly successiveprints with excellent pattern quality and useful feature size accuracy.Coupled with the target stamping times, the concentration rangedescribed above was discovered to be useful for patterns comprising alow density region, for example a low density region comprising finescale features as described above. Preferably, the pressure appliedduring printing, after application of the stamp to the substrate, isbetween 0 and 10 kilopascals, with respect to the actual area of contactbetween the stamp and the substrate. The process windows described abovefor octadecylthiol and for patterns comprising a low density region, forexample with fine features, is regarded as useful for othermonolayer-forming molecules that are 18 atoms long (not including thehead group, for example a thiol head group, not hydrogen atoms) or thatshare critical printing attributes with octadecylthiol. Octadecylthioland like molecules are preferred to hexadecylthiol and like molecules.

The ranges of concentration, and in particular for the SAM-formingmolecules noted above, were in part also determined based on the need toavoid undesirable precipitation of the SAM-forming molecules on thesurface of the stamp or within the stamp. It was discovered that certainconcentrations, in particular high concentrations (e.g., 10 mMoctadecylthiol in PDMS) although useful for printing can developundesirable precipitation during extended and repeated use, the focus ofthe present disclosure. This issue of precipitation is especiallyproblematic for eicosanethiol (20 carbon chain thiol), although not tothe extent that the molecule cannot be used.

The aforementioned specification of SAM-forming molecules andconcentration, especially for the preferred molecules, lead to an inkedstamp that is especially capable of generating SAM-based masks of theaforementioned geometries with high throughput, especially on metalizedpolymer film substrates. The inked stamps have been found to bepreferred for stamping or printing the SAM masks at commerciallyattractive print times for the geometries noted, optimally addressingthe need for adequate SAM perfection to be useful as an etch mask andlimited SAM spreading, preferably for particular substrates, for examplepolymer film substrates. According to the invention, the time of contactbetween the stamp and the metal surface (print time) lies between 0.1and 30 seconds, preferably between 0.1 and 10 seconds, more preferablybetween 0.5 and 5 seconds.

The above-described process of stamping or printing with theabove-described stamp can be carried out with any level of pressurebetween the stamp and the substrate that does not result in collapse.Examples of useful levels of pressure include less than 100 kilopascals,less than 50 kilopascals, less than 25 kilopascals, or even less than 10kilopascals. The methods described herein are particularly useful forgenerating metal patterns by microcontact printing without theapplication of significant pressure. Applying increased pressure canimprove the quality of SAM transfer, and thus generation of a betteretch mask, but can compromise pattern fidelity due to stamp distortion.

The inked stamp and the printing conditions described above areparticularly useful for carrying out repeated stampings of SAM-basedetch mask patterns of the aforementioned geometries. By repeatedstampings, what is meant is that once the stamp is inked, the stamp canbe used repeatedly to generate the printed etch mask on new metalsurface regions, for example new pieces of metalized substrate. Theinked stamps are useful for carrying out greater than 5, or greater than10, or greater than 20, or greater than 30, or greater than 40, orgreater than 50 prints without repeating the inking step. The timebetween prints for such repeated printing, using the aforementionedstamps, with their relief patterns and ink concentrations, is preferablyshort, for example less than 30 seconds, or less than 15 seconds, orless than 10 seconds, or less than 5 seconds.

For patterns including junctions between low density regions and largerfeatures, wherein linear features or elements in the low-density regionmake contact to the larger features, some pattern geometries includewidening the linear feature before it makes contact to the largerfeature. For example, a 1 to 5 μm wide linear element making contact toa large feature can be tapered to down to such width over a length of 1to 10 times its width, from the larger feature. The tapering can assistin maintaining effective patterning. For some inking and printingparameters, portions of such narrow linear elements making contact tolarge features can be inadequately protected by the printed SAM duringetching, leading to degradation of the linear element near to the largerfeature.

Useful visible light transparent substrates include polymeric films.Useful polymeric films include thermoplastic and thermoset polymericfilms. Examples of thermoplastics include polyolefins, polyacrylates,polyamides, polyimides, polycarbonates, and polyesters. Further examplesof thermoplastics include polyethylene, polypropylene,poly(methylmethacrylate), polycarbonate of bisphenol A, poly(vinylchloride), polyethylene terephthalate, and poly(vinylidene fluoride).

Metal-coated visible light transparent substrate include a polymericfilm, described above, having an inorganic material coating (e.g.,metallic coating) on the polymeric film substrate to support theself-assembled monolayer, and in turn be patterned by etching. Theinorganic coating can include, for example, elemental metal, metalalloys, intermetallic compounds, metal oxides, metal sulfides, metalcarbides, metal nitrides, and combinations thereof. Exemplary inorganicsurfaces for supporting self-assembled monolayers include gold, silver,palladium, platinum, rhodium, copper, nickel, iron, indium, tin,tantalum, as well as mixtures, alloys, and compounds of these elements.The inorganic coatings on the polymeric substrate can be any thicknesssuch as, for example, from 1 to 3000 nanometers (nm). The inorganicmaterial coating can be deposited using any convenient method, forexample sputtering, evaporation, chemical vapor deposition, or chemicalsolution deposition (including electroless plating).

The advantageous pattern geometries, inking conditions, and printingconditions described above have been identified as such for particularmetals to be patterned subsequently by etching. The preferred metals aresilver, gold, and palladium, although it is within the scope of theinvention to etch pattern other metals. The SAM masks generatedaccording to the invention are particularly useful for etch patterningthe aforementioned metals at thickness between 5 and 1000 nm, or between10 and 500 nm, or between 15 and 200 nm, or between 20 and 100 nm. Themetal can be deposited on a substrate, before patterning, by any knowndeposition method, including vapor phase methods such as sputtering orevaporation, or by solution methods such as electroless plating. Theetching can be carried out using methods known in the art.

In some embodiments, the method for forming a metal pattern includes areversal of the relief relationship between stamp or plate andsubstrate, versus the foregoing discussion. That is, in theseembodiments, the relief pattern formerly described for the stamp asuseful are characteristic of the substrate, and the stamp is essentiallyfeatureless. In all other aspects, including pattern geometry, metal,inking, and print time for example, these embodiments are the same asthose described above for use of relief structured stamps or plates andflat substrates. An example of a useful metalized relief-structuredsubstrate is a silver vapor-coated, microreplicated polymer film. Athiol-infused stamp (e.g., PDMS) or rotary printing plate, for examplethat includes no relief structure, can be used to transfer aself-assembled monolayer mask to the raised regions of theconductor-coated relief pattern of the substrate surface. In asubsequent step, the conductor is selectively etched from the regionscomplementary to the raised features of the relief pattern, yielding aconductor pattern according to the raised feature pattern.

FIG. 13 illustrates a schematic diagram of a touch screen sensor 100.The touch screen sensor 100 includes a touch screen panel 110 having atouch sensing area 105. The touch sensing area 105 is electricallycoupled to a touch sensor drive device 120. The touch screen panel 110is incorporated into a display device.

FIG. 14 illustrates a perspective view of a conductive visible lighttransparent region 301 lying within the touch sensing area 305. Theconductive visible light transparent region 301 includes a visible lighttransparent substrate 330 and an electrically conductive micropattern340 disposed on or in the visible light transparent substrate 330. Thevisible light transparent substrate 330 includes a major surface 332 andis electrically insulating. The visible light transparent substrate 330can be formed of any useful electrically insulating material such as,for example, glass or polymer. Examples of useful polymers for lighttransparent substrate 330 include polyethylene terephthalate (PET) andpolyethylene naphthalate (PEN). The electrically conductive micropattern340 can be formed of a plurality of linear metallic features formedaccording to the method described herein.

FIG. 14 also illustrates an axis system for use in describing theconductive visible light transparent region 301 lying within the touchsensing area 305. Generally, for display devices, the x and y axescorrespond to the width and length of the display and the z axis istypically along the thickness (i.e., height) direction of a display.This convention will be used throughout, unless otherwise stated. In theaxis system of FIG. 14, the x axis and y axis are defined to be parallelto a major surface 332 of the visible light transparent substrate 330and may correspond to width and length directions of a square orrectangular surface. The z axis is perpendicular to that major surfaceand is typically along the thickness direction of the visible lighttransparent substrate 330. A width of the plurality of linear metallicfeatures that form the electrically conductive micropattern 340correspond to an x-direction distance for the parallel linear metallicfeatures that extend linearly along the y axis and a y-directiondistance for the orthogonal linear metallic features correspond to awidth of the orthogonal linear metallic features. A thickness or heightof the linear metallic features corresponds to a z-direction distance.

In some embodiments, the conductive visible light transparent region 301lying within the touch sensing area 305 includes two or more layers ofvisible light transparent substrate 330 having a conductive micropattern340.

The conductive micropattern 340 is deposited on the major surface 332.Because the sensor is to be interfaced with a display to form a touchscreen display, or touch panel display, the substrate 330 is visiblelight transparent and substantially planar. The substrate and the sensormay be substantially planar and flexible. By visible light transparent,what is meant is that information (for example, text, images, orfigures) that is rendered by the display can be viewed through the touchsensor. The viewability and transparency can be achieved for touchsensors including conductors in the form of a deposited metal, evenmetal that is deposited with thickness great enough to block light, ifthe metal is deposited in an appropriate micropattern.

The conductive micropattern 340 includes at least one visible lighttransparent conductive region overlaying a viewable portion of thedisplay that renders information. By visible light transparentconductive, what is meant is that the portion of the display can beviewed through the region of conductive micropattern and that the regionof micropattern is electrically conductive in the plane of the pattern,or stated differently, along the major surface of the substrate ontowhich the conductive micropattern is deposited and to which it isadjacent. Preferred conductive micropatterns include regions with twodimensional meshes, for example square grids or regular hexagonalnetworks, where conductive traces define enclosed open areas within themesh that are not deposited with conductor that is in electrical contactwith the traces of the mesh. The open spaces and associated conductortraces at their edges are referred to herein as cells. Other usefulgeometries for mesh cells include random cell shapes and irregularpolygons.

In one illustrative embodiment, a method of manufacturing a touch screensensor is provided, the method including providing a metal-coatedvisible light transparent substrate having a relief pattern with raisedfeatures, the relief pattern having a low density region measuring atleast 5 mm². The low density region has an average area density value ofraised features between 0.5 to 10%, linear segments having a width valuebetween 0.5 to 25 μm, and a distance value between adjacent raisedfeatures of less than 1 mm. The method includes contacting an inkedelastomeric stamp inked with self-assembled monolayer-forming moleculesto the metal-coated visible light transparent substrate and then etchingthe metal to form an electrically conductive micropattern on the visiblelight transparent substrate raised features.

In another illustrative embodiment, a method of patterning a conductoron a substrate is provided, the method including providing an inkedstamp with a relief pattern with raised features, the inked stampcomprising linear organosulfur self-assembled monolayer-formingmolecules with chain length from 16 to 18 atoms at a concentrationwithin the stamp of 1 to 10 mM, the relief pattern having a low densityregion measuring at least 5 mm². The low density region has an averagearea density value of raised features between 0.5 to 5%, linear segmentshaving a width value from approximately 1 to 4 μm, a distance valuebetween adjacent raised features of less than 1 mm, and a raised featuremeasuring at least 25 μm in width. The method includes contacting theinked stamp to a metal-coated visible light transparent substrate, thecontacting step having a contact time in a range from 0.5 to 10 seconds,thereby depositing a pattern of self-assembled monolayer. The methodalso includes etching the metal to form a transparent electricallyconductive micropattern corresponding to the raised features of theinked stamp on the visible light transparent substrate.

In another illustrative embodiment, a method of patterning a conductoron a substrate is provided, the method including providing an inkedstamp with a relief pattern with raised features, the inked stampcomprising linear organosulfur self-assembled monolayer-formingmolecules with chain length from 16 to 18 atoms at a concentrationwithin the stamp of 1 to 10 mM, the relief pattern having a low densityregion measuring at least 5 mm². The low density region has an averagearea density value of raised features between 0.5 to 5%, linear segmentshaving a width value from approximately 1 to 4 μm, a distance valuebetween adjacent linear segments of less than 1 mm, and a raised featuremeasuring at least 150 μm in width. The method includes contacting theinked stamp to a metal-coated visible light transparent substrate, thecontacting step having a contact time in a range from 0.5 to 10 seconds,thereby depositing a pattern of self-assembled monolayer. The methodalso includes etching the metal to form a transparent electricallyconductive micropattern corresponding to the raised features of theinked stamp on the visible light transparent substrate.

In another illustrative embodiment, a method of patterning a conductoron a substrate is provided, the method including providing an inkedstamp with a relief pattern with raised features, the inked stampcomprising linear organosulfur self-assembled monolayer-formingmolecules comprising octadecylthiol at a concentration within the stampof 1 to 10 mM, the relief pattern having a low density region measuringat least 5 mm². The low density region has an average area density valueof raised features between 0.5 to 5%, linear segments having a widthvalue from approximately 1 to 4 μm, a distance value between adjacentlinear segments of less than 1 mm, and a raised feature measuring atleast 150 μm in width. The method includes contacting the inked stamp toa metal-coated visible light transparent substrate, the contacting stephaving a contact time in a range from 0.5 to 10 seconds, therebydepositing a pattern of self-assembled monolayer. The method alsoincludes etching the metal to form a transparent electrically conductivemicropattern corresponding to the raised features of the inked stamp onthe visible light transparent substrate.

In another illustrative embodiment, a method of patterning a conductoron a substrate is provided, the method including providing an inkedstamp with a relief pattern with raised features, the inked stampcomprising linear organosulfur self-assembled monolayer-formingmolecules comprising octadecylthiol at a concentration within the stampof 1 to 10 mM, the relief pattern having a low density region measuringat least 5 mm². The low density region has an average area density valueof raised features between 0.5 to 5%, linear segments having a widthvalue from approximately 1 to 4 μm, a distance value between adjacentlinear segments of less than 1 mm, and a raised feature measuring atleast 150 μm in width. The method includes contacting the inked stamp toa metal-coated visible light transparent substrate, the contacting stephaving a contact time in a range from 0.5 to 5 seconds, therebydepositing a pattern of self-assembled monolayer. The method alsoincludes etching the metal to form a transparent electrically conductivemicropattern corresponding to the raised features of the inked stamp onthe visible light transparent substrate.

In another illustrative embodiment, a method of patterning a conductoron a substrate is provided, the method including providing an inkedstamp with a relief pattern with raised features, the inked stampcomprising linear organosulfur self-assembled monolayer-formingmolecules comprising octadecylthiol at a concentration within the stampof 1 to 10 mM, the relief pattern having a low density region measuringat least 5 mm². The low density region has an average area density valueof raised features between 0.5 to 5%, linear segments having a widthvalue from approximately 1 to 4 μm, a distance value between adjacentlinear segments of less than 1 mm, and a raised feature measuring atleast 0.25 mm in width. The method includes contacting the inked stampto a metal-coated visible light transparent substrate, the contactingstep having a contact time in a range from 0.5 to 5 seconds, therebydepositing a pattern of self-assembled monolayer. The method alsoincludes etching the metal to form a transparent electrically conductivemicropattern corresponding to the raised features of the inked stamp onthe visible light transparent substrate.

EXAMPLES Stamp Fabrication

Two different master tools for molding elastomeric stamps were generatedby preparing patterns of photoresist (Shipley1818, Rohm and HaasCompany, Philadelphia, Pa.) on 10 centimeter (cm) diameter siliconwafers. The different master tools were based on two different patterndesigns, herein referred to as design “V1” and design “V2.” The designshad some common elements and some differences. Both designs measured 5cm by 5 cm in total area and included a 1 mm wide frame (open area inmasks below and raised feature in the stamps below). Both designs alsoincluded a series of 20 low density mesh bars measuring approximately 33mm in length and had width values ranging from 0.8 to 1.2 mm, the barsbeing terminated with 2 mm by 2 mm contact pads. In addition to theframe, the mesh bars, and the pads, the two designs included isolatedfeatures in the space between the mesh bars and between the mesh barsand the frame. The isolated features were variously sized and shapedforms with minimum dimension in the size range of 3 to 100 μm. Thedesign V1 had an aggregate quantity of open area in the mask and thusraised area on the resulting stamp of 5.95 cm². The design V2 had anaggregate quantity of open area in the mask and thus raised area on theresulting stamp of 4.37 cm². To fabricate a master, the photoresist wasspin-cast onto the wafer to a thickness of approximately 1.8 μm. Foreach master tool, a separate binary chrome photomask with openings inthe chrome that define a low density pattern of line segments togetherwith 2 mm by 2 mm square pads was used to expose the photoresist forpatterning. After development of the photoresist, a master tool wasprovided that included a binary relief pattern comprising recessedfeatures in the form of a low density area distribution of line segmentsand the pads. For both master tools, the portion of the patterncomprising the low density area distribution of line segments includeddifferent low density mesh geometries (for example, square grids) with 3μm and 5 μm widths for the traces that define the meshes. The open areavalues for selected mesh regions were 90%, 93%, 95%, and 97% (i.e., 10,7, 5, and 3% feature density, respectively). FIG. 8 is a scanningelectron photomicrograph of a portion of a completed pattern,illustrating the arrangement of two-dimensional mesh regions of highopen area and a 2 mm by 2 mm pad. FIG. 9 and FIG. 10 are scanningelectron photomicrographs of a completed pattern (thin film silver onPET), illustrating the geometries of two low-density two-dimensionalmicropattern regions (square cell geometry with 95% open area and 5 μmwide traces, hexagonal cell geometry with 97% open area and three μmwide traces, respectively). An elastomeric stamp was molded against themaster tool by pouring uncured polydimethylsiloxane (PDMS, Sylgard™ 184,Dow Corning, Midland, Mich.) over the tool to a thickness ofapproximately 3.0 mm. The uncured silicone in contact with the masterwas degassed by exposing to a vacuum, and then cured for 2 hours at 70°C. After peeling from the master tool, a PDMS stamp was provided with arelief pattern comprising raised features approximately 1.8 μm inheight, in the pattern comprising the low density area distribution ofline segments and the pads. The stamp was cut to a size of approximately5 by 5 cm.

Inking

The stamp was inked by contacting its back side (major surface withoutrelief pattern) to a solution of alkylthiol in ethanol for a prescribedtime (inking time). The alkylthiol molecules used were hexadecylthiol(“HDT” H0068, TCI America, Wellesley Hills, Mass.) and octadecylthiol(“ODT” 00005, TCI AMERICA). The concentration of alkylthiol solution andthe inking time were selected to achieve a target concentration of alkylthiol in the PDMS stamp adjacent to the printing surface, as determinedusing a finite difference simulation computer program and measureddiffusion coefficient values. For HDT, the diffusion coefficient valuethat was used for the simulations was 6.6E-7 cm² per second, a knownvalue for HDT diffusion in ethanol-swelled PDMS. For ODT, two differentvalues of diffusion coefficient were used for simulations, in order tobracket a range of expected thiol concentrations in the stamp adjacentto the printing surface. The two values for ODT were 4.0E-7 cm² persecond, a known value for ODT diffusion in PDMS, and 6.6E-7 cm² persecond, the known diffusion coefficient for HDT in ethanol-swelled. Thevalues of the diffusion coefficient for ODT that were used areconsidered the lowest and the highest possible values that woulddescribe the transport of octadecylthiol in the PDMS within the examplesthat follow. Thus, the calculations allowed for the bracketing of arange of expected concentration for the octadecylthiol adjacent to theprinting surface in the examples. Thus, in the examples that follow,individual values of concentration are reported for hexadecylthiol andranges of concentration values are reported for octadecylthiol.

Stamping

Metalized polymer film substrates were stamped after inking of thestamp. In each case, the film substrate was polyethyleneterephthalate“PET” (ST504, DuPont, Wilmington, Del.). The substrate was first coatedby thermal evaporation (DV-502A, Denton Vacuum, Moorestown, N.J.) withmetal thin films. For all examples, the substrate surface was firstcoated with 20 angstroms of chromium and then coated with 100 nm ofsilver or gold. After metallization, the films were stamped with inkedstamps as described above. The metalized film substrates measuredapproximately 6 by 6 cm in area. For stamping, the metalized film wascontacted to the stamp relief patterned-surface, which was face up, byfirst contacting an edge of the film sample to the stamp surface andthen rolling the film into contact across the stamp, using a handheldrubber roller with diameter of approximately 3.5 cm. The rolling steprequired less than one second to execute. In the examples that follow, astamping time is given, the stamping time corresponding to additionalcontact time between the substrate and the stamp after rolling thesubstrate onto the stamp. After the specified time had elapsed, thesubstrate was peeled from the stamp, a step that required less than 1second. In some cases, as noted below, an additional mass was applied tothe substrate-stamp assembly, after application of the substrate to thestamp and during stamping. The additional mass was a flat piece of glassweighing 120 grams plus a piece of flat ceramic tile with mass 140grams, for a total of 260 grams. With respect to pattern design V1, withits contact area during stamping of 5.95 cm², 260 grams of applied masscorresponds to an applied pressure between the substrate and the raisedfeatures of the stamp of 4.3 kilopascals. With respect to pattern designV2, with its contact area during stamping of 4.37 cm², 260 grams ofapplied mass corresponds to an applied pressure between the substrateand the raised features of the stamp of 5.8 kilopascals.

Etching

After stamping, the metalized film substrate with printed pattern wasimmersed into an etchant solution for selective etching and metalpatterning. For printed metalized film substrates bearing a gold thinfilm, the etchant comprised 1 gram of thiourea (T8656, Sigma-Aldrich,St. Louis, Mo.), 0.54 milliliter of concentrated hydrochloric acid(HX0603-75, EMD Chemicals, Gibbstown, N.J.), 0.5 milliliter of hydrogenperoxide (30%, 5240-05, Mallinckrodt Baker, Phillipsburg, N.J.), and 21grams of deionized water. To pattern the gold thin film, the printedmetalized film substrate was immersed in the etch solution for 50seconds. For printed metalized film substrates bearing a silver thinfilm, the etchant comprised 0.45 grams of thiourea (T8656,Sigma-Aldrich, St. Louis, Mo.), 1.64 grams of ferric nitrate (216828,Sigma-Aldrich, St. Louis, Mo.), and 200 milliliter of deionized water.To pattern the silver thin film, the printed metalized film substratewas immersed in the etch solution for 3 minutes. After patterned etchingof the gold or silver, residual chromium was etched using a solution of2.5 grams of potassium permanganate (PX1551-1, EMD Chemicals), 4 gramsof potassium hydroxide (484016, Sigma-Aldrich), and 100 milliliters ofdeionized water.

Characterization

After selective etching and metal patterning, the metal patterns werecharacterized using an optical microscope (Model BH-2 equipped with aDP12 digital camera, Olympus America, Center Valley, Pa.), scanningelectron microscope (SEM, Model JSM-6400, JEOL Ltd, Tokyo, Japan), andresistance meter (GoldStar DM-313, LG Precision Co. Ltd., Korea). Themicroscopic techniques were used to determine the fidelity with whichthe intended pattern had been generated for the thin film metal afteretching. The width of line features in the metal pattern was measuredand compared with nominal width values of 3 μm and 5 μm. A dimensionaccuracy quality factor of 5, 4, 3, 2, or 1 was assigned, depending onwhether the size of the printed feature exceeds the nominal size by 0μm, approximately >0 to ≦0.5 μm, approximately >0.5 to ≦1.0 μm,approximately >1.0 to ≦1.5 μm, or >1.5 μm, respectively. The selectivityof etching was also judged using the microscopic techniques for thelarge pad regions (2 mm by 2 mm). A large feature selectivity qualityfactor of 1, 2, 3, 4, or 5 was assigned to describe the degree ofselectivity that occurred in etch-patterning the larger area pads (5 ishighest quality—essentially no pinholes or erosion of the pads duringetching; 1 is lowest quality—the pad was largely etched away during theetch-patterning step). By selectivity, what is meant is the degree ofprotection and preservation of the metal, in the pad regions forexample, during the etching removal of unprinted regions. For eachquality factor above, it is preferable to achieve a value of 3, morepreferably to achieve a value of 4, and even more preferable to achievea value of 5. The resistance meter was used to measure the resistance ofisolated mesh regions measuring approximately 1 mm by approximately 33mm, between the large pads (2 mm by 2 mm). Based on this geometry of themesh regions, a value of sheet resistance for each mesh was determined(equal to the measured resistance divided by 33 (squares)).

Example 1

An electrically conductive micropattern (V1) of thin film silver wasfabricated and characterized according to the procedures describedabove. The ink solution comprised hexadecylthiol dissolved in ethanol ata concentration of 10 mM. The ink solution was contacted to the backside of the stamp for 2.3 hours, leading to a hexadecylthiolconcentration in the PDMS adjacent to the printing or stamping surfaceof approximately 0.8 mM. The stamping time was 10 seconds and there wasan applied mass of 260 g during stamping. FIG. 11 gives an SEMphotomicrograph recorded from the completed thin film metalmicropattern, derived from a low-density region comprising a hexagonalmesh with 97% open area and target trace width of 3 μm. The actual tracewidth measured over 5 μm.

Example 2

An electrically conductive micropattern (V2) of thin film silver wasfabricated and characterized according to the procedures describedabove. The ink solution comprised hexadecylthiol dissolved in ethanol ata concentration of 10 mM. The ink solution was contacted to the backside of the stamp for 17.5 hours, leading to a hexadecylthiolconcentration in the PDMS adjacent to the printing or stamping surfaceof approximately 5 mM. The stamping time was 5 seconds and there was nomass applied to the substate-stamp assembly after rolling application ofthe substrate to the stamp. FIGS. 8, 9, and 10 give SEM photomicrographsrecorded from the completed thin film metal micropattern. FIG. 12 isanother SEM photomicrograph of the completed thin film silvermicropattern, derived from a low-density region comprising a hexagonalmesh with 97% open area and target trace width of 3 μm. The actual tracewidth measured approximately 3.2 μm.

Examples 3-42

Electrically conductive micropatterns of thin film silver werefabricated according to the process parameters listed in Table 1. Tables2-7 give the quality factors assigned to selected examples, per thedescriptions of quality factors given above. Examples that are notrepresented in Tables 2-7 are Examples 3, 4, 23 and 24, for which thestamping and etching steps yielded a very poorly defined pattern. ForExample 38, a low density mesh region (square grid with 5 μm wide tracesand 10% fill factor) of the conductor micropattern, measuring 1 mm inwidth and 33 mm in length and terminated at each end with a 2 mm by 2 mmpad, exhibited a resistance of 229 ohms. The resistance readingcorresponds to a sheet resistance for the visible light transparent meshregion of 229/33=7 ohms per square. For Example 38, a low density meshregion (square grid with 3 μm wide traces and 5% fill factor) of theconductor micropattern, measuring 1 mm in width and 33 mm in length andterminated at each end with a 2 mm by 2 mm pad, exhibited a resistanceof 419 ohms. The resistance reading corresponds to a sheet resistancefor the visible light transparent mesh region of 419/33=12.7 ohms persquare. For Example 38, a low density mesh region (square grid with 3 μmwide traces and 3% fill factor) of the conductor micropattern, measuring1 mm in width and 33 mm in length and terminated at each end with a 2 mmby 2 mm pad, exhibited a resistance of 624 ohms. The resistance readingcorresponds to a sheet resistance for the visible light transparent meshregion of 624/33=18.9 ohms per square. For Example 38, an approximately1 cm diameter circular region that included the 3% and 5% fill factormesh regions for which sheet resistance measurements are reported abovewas measured for its visible light transmittance. The measurement wasmade with an optical densitometer with photopic correction (JonathanAllen, Titusville, N.J.). For the circular area just described thevisible light transmittance was approximately 85%, as compared with ameasurement of 88.7% for the base film substrate, suggesting an averagefill factor over the 1 cm diameter circular area of approximately 4%(open area of approximately 96%).

Example 43

An electrically conductive micropattern (V1) of thin film gold wasfabricated and characterized according to the procedures describedabove. The ink solution comprised octadecylthiol dissolved in ethanol ata concentration of 10 mM. The ink solution was contacted to the backside of the stamp for 4.5 hours, leading to an octadecylthiolconcentration in the PDMS adjacent to the printing or stamping surfaceof approximately 0.8 mM. The stamping time was 2 seconds and there wasno mass applied to the substate-stamp assembly after rolling applicationof the substrate to the stamp. A low density mesh region (square gridwith 3 μm wide traces and 3% fill factor) of the conductor micropattern,measuring 1 mm in width and 33 mm in length and terminated at each endwith a 2 mm by 2 mm pad, exhibited a resistance of 685 ohms. Theresistance reading corresponds to a sheet resistance for the visiblelight transparent mesh region of 685/33=20.8 ohms per square.

TABLE 1 Thiol Thiol Contact time concentration Applied concentrationbetween stamp in stamp adjacent Stamping mass during Example in inksolution and ink solution to printing time stamping number Pattern Thiol(mM) (hours) surface (mM) (seconds) (grams) 3 V2 HDT 10 1 0.0003 10 0 4V2 HDT 10 1 0.0003 10 260 5 V2 HDT 10 2 0.042 10 0 6 V2 HDT 10 2 0.04210 260 7 V2 HDT 10 2.3 0.082 1 0 8 V2 HDT 10 2.3 0.082 5 0 9 V2 HDT 102.3 0.082 10 0 10 V2 HDT 10 2.3 0.082 10 260 11 V2 HDT 10 3.5 0.4 1 0 12V2 HDT 10 3.5 0.4 10 0 13 V2 HDT 10 3.5 0.4 10 260 14 V2 HDT 10 4.5 0.81 0 15 V2 HDT 10 4.5 0.8 5 0 16 V2 HDT 10 4.5 0.8 10 0 17 V2 HDT 10 4.50.8 10 260 18 V2 HDT 10 17.5 5 5 0 19 V2 HDT 50 4.5 10 10 260 20 V2 HDT50 24 >25 0 0 21 V2 HDT 50 24 >25 1 0 22 V2 HDT 50 24 >25 5 0 23 V1 ODT10 1 0.00001-0.001  10 0 24 V1 ODT 10 1 0.00001-0.001  10 260 25 V1 ODT10 2 0.0075-0.082 10 0 26 V1 ODT 10 2 0.0075-0.082 10 260 27 V1 ODT 102.3 0.018-0.15 1 0 28 V1 ODT 10 2.3 0.018-0.15 5 0 29 V1 ODT 10 2.30.018-0.15 10 0 30 V1 ODT 10 2.3 0.018-0.15 10 260 31 V1 ODT 10 3.5 0.14-0.60 1 0 32 V1 ODT 10 3.5  0.14-0.60 10 0 33 V1 ODT 10 3.5 0.14-0.60 5 260 34 V1 ODT 10 4.5 0.35-1.1 1 0 35 V1 ODT 10 4.5 0.35-1.15 0 36 V1 ODT 10 4.5 0.35-1.1 10 0 37 V1 ODT 10 4.5 0.35-1.1 10 260 38V2 ODT 20 24 >10 1 0 39 V2 ODT 20 24 >10 5 0 40 V2 ODT 20 24 >10 10 0 41V2 ODT 20 24 >10 20 0 42 V2 ODT 20 24 >10 5 260

TABLE 2 Large feature selectivity quality factor (0 g applied mass)Concentration of hexadecylthiol in stamp adjacent to stamping Stampingtime (seconds) surface (mM) 1 5 10 0.042 N//A N//A 1 0.082 2 2 2 0.4 2N//A 3 0.8 3 5 5 5 N//A 5 N//A 10 N//A N//A 5 >25 5 5 N//A

TABLE 3 Low density region dimension accuracy quality factor (0 gapplied mass) Concentration of hexadecylthiol in stamp adjacent tostamping Stamping time (seconds) surface (mM) 1 5 10 0.042 N/A N/A 50.082 5 5 5 0.4 5 N/A 5 0.8 5 3 3 5 N/A 4 N/A 10 N/A N/A 1 >25 1 1 N/A

TABLE 4 260 grams of applied mass (10 seconds stamping time)Concentration of hexadecylthiol in stamp Large feature Low-densityregion adjacent to stamping selectivity quality dimension accuracysurface (mM) factor quality factor 0.042 1 5 0.082 2 4 0.4 4 4 0.8 5 110 5 1

TABLE 5 Large feature selectivity quality factor (0 g applied mass)Concentration of octadecylthiol in stamp Stamping time (seconds)adjacent to stamping surface (mM) 1 5 10 20 0.0075-0.082 N/A N/A 1 N/A0.018-0.15 2 2 2 N/A  0.14-0.60 3 N/A 3 N/A 0.35-1.1 3 4 5 N/A >10 5 5 55

TABLE 6 Low-density region dimension accuracy quality factor (0 gapplied mass) Concentration of octadecylthiol in stamp Stamping time(seconds) adjacent to stamping surface (mM) 1 5 10 20 0.0075-0.082 N/AN/A 5 N/A 0.018-0.15 5 5 5 N/A  0.14-0.60 5 N/A 5 N/A 0.35-1.1 5 5 5N/A >10 4 5 3 2

TABLE 7 260 grams of applied mass Concentration of Large Low-densityoctadecylthiol in feature region stamp adjacent to selectivity dimensionStamping time stamping surface quality accuracy (seconds) (mM) factorquality factor 10 0.0075-0.082 1 5 10 0.018-0.15 2 5 5  0.14-0.60 4 4 100.35-1.1 5 3 5 >10 5 1

Example 43

A transparent sensor element was fabricated and combined with a touchsensor drive device as generally shown in FIGS. 15, 16 and 17 usingmicrocontact printing and etching. The device was then integrated with acomputer processing unit connected to a display to test the device. Thedevice was able to detect the positions of multiple single and orsimultaneous finger touches, which was evidenced graphically on thedisplay.

Formation of a Transparent Sensor Element

First Patterned Substrate

A first visible light substrate made of polyethylene terephthalate (PET)having a thickness of 125 μm was vapor coated with 100 nm silver thinfilm using a thermal evaporative coater to yield a first silvermetalized film. The PET was commercially available as product numberST504 from E.I. du Pont de Nemours, Wilmington, Del. The silver wascommercially available from Cerac Inc., Milwaukee, Wis. as 99.99% pure 3mm shot.

A first poly(dimethylsiloxane) stamp, referred to as PDMS andcommercially available as product number Sylgard 184, Dow Chemical Co.,Midland, Mich., having a thickness of 3 mm, was molded against a 10 cmdiameter silicon wafer (sometimes referred to in the industry as a“master”) that had previously been patterned using standardphotolithography techniques. The PDMS was cured on the silicon wafer at65° C. for 2 hours. Thereafter, the PDMS was peeled away from the waferto yield a first stamp having two different low-density regions withpatterns of raised features, a first continuous hexagonal mesh patternand a second discontinuous hexagonal mesh pattern. That is, the raisedfeatures define the edges of edge-sharing hexagons. A discontinuoushexagon is one that contains selective breaks in a line segment. Theselective breaks had a length less than 10 μm. The breaks were designedand estimated to be approximately 5 μm. In order to reduce theirvisibility, it found that, preferably, the breaks should be less than 10μm, more preferably, 5 μm or less, e.g., between 1 and 5 μm. Each raisedhexagon outline pattern had a height of 2 μm, had 1% to 3% areacoverage, corresponding to 97% to 99% open area, and line segments thatmeasured from 2 to 3 μm in width. The first stamp also included raisedfeatures defining 500 μm wide traces. The first stamp has a firststructured side that has the hexagonal mesh pattern regions and thetraces and an opposing second substantially flat side.

The stamp was placed, structured side up, in a glass Petri dishcontaining 2 mm diameter glass beads. Thus, the second, substantiallyflat side was in direct contact with the glass beads. The beads servedto lift the stamp away from the base of the dish, allowing the followingink solution to contact essentially all of the flat side of the stamp. A10 millimolar ink solution of 1-octadecanethiol (product number C18H3CS,97%, commercially available from TCI America, Portland Oreg.) in ethanolwas pipetted into the Petri dish beneath the stamp. The ink solution wasin direct contact with the second substantially flat side of the stamp.After sufficient inking time (e.g., 3 hours) where the ink has diffusedinto the stamp, the first stamp was removed from the petri dish. Theinked stamp was placed, structured side up, onto a working surface. Thefirst silver metalized film was applied using a hand-held roller ontothe now inked structured surface of the stamp such that the silver filmwas in direct contact with the structured surface. The metalized filmremained on the inked stamp for 15 seconds. Then the first metalizedfilm was removed from the inked stamp. The removed film was placed forthree minutes into a silver etchant solution, which contained (i) 0.030molar thiourea (product number T8656, Sigma-Aldrich, St. Louis, Mo.) and(ii) 0.020 molar ferric nitrate (product number 216828, Sigma-Aldrich)in deionized water. After the etching step, the resulting firstsubstrate was rinsed with deionized water and dried with nitrogen gas toyield a first patterned surface. Where the inked stamp made contact withthe silver of the first metalized substrate, the silver remained afteretching. Thus silver was removed from the locations where contact wasnot made between the inked stamp and silver film.

FIGS. 15, 15 a and 15 b show a first patterned substrate 700 having aplurality of first continuous regions 702 alternating between aplurality of first discontinuous regions 704 on a first side of thesubstrate, which is the side that contained the now etched and patternedsilver metalized film. The substrate has an opposing second side that issubstantially bare PET film. Each of the first regions 702 has acorresponding 500 μm wide conductive trace 706 disposed at one end. FIG.15 a shows an exploded view of the first region 702 having a pluralityof continuous lines forming a hexagonal mesh structure. FIG. 15 b showsan exploded view of the first discontinuous region 704 having aplurality of discontinuous lines (shown as selective breaks in eachhexagon) forming a discontinuous hexagonal mesh structure. Each meshstructure of regions 702 and 704 had 97% to 99% open area. Each linesegment measured from 2 to 3 μm.

Second Patterned Substrate

The second patterned substrate was made as the first patterned substrateusing a second visible light substrate to produce a second silvermetalized film. A second stamp was produced having a second continuoushexagonal mesh pattern interposed between a second discontinuoushexagonal mesh pattern.

FIGS. 16, 16 a and 16 b show a second patterned substrate 720 having aplurality of second continuous regions 722 alternating between aplurality of second discontinuous regions 724 on a first side of thesecond substrate. Each of the second regions 722 has a corresponding 500μm wide second conductive trace 726 disposed at one end. FIG. 20 a showsan exploded view of one second region 722 having a plurality ofcontinuous lines forming a hexagonal mesh structure. FIG. 20 b shows anexploded view of one second discontinuous region 724 having a pluralityof discontinuous lines (shown as selective breaks in each hexagon)forming discontinuous hexagonal mesh structure. The selective breaks hada length less than 10 μm. The breaks were designed and estimated to beapproximately 5 μm. In order to reduce their visibility, it found that,preferably, the breaks should be less than 10 μm, more preferably, 5 μmor less, e.g., between 1 and 5 μm. Each mesh structure of region 722 and724 had 97% to 99% open area. Each line segment measured from 2 to 3 μm.

Formation of a Projected Capactive Touch Screen Sensor Element

The first and second patterned substrates made above were used toproduce a two-layer projected capacitive touch screen transparent sensorelement as follows.

The first and second patterned substrates were adhered together usingOptically Clear Laminating Adhesive 8141 from 3M Company, St. Paul,Minn. to yield a multilayer construction. A handheld roller was used tolaminate the two patterned substrates with the regions of the first andsecond conductive trace regions 706 and 726 being adhesive free. Themultilayer construction was laminated to a 0.7 mm thick float glassusing Optically Clear Laminating Adhesive 8141 such that the first sideof the first substrate was proximate to the float glass. The adhesivefree first and second conductive trace regions 706 and 726 allowedelectrical connection to be made to the first and second patternedsubstrates 700 and 720.

FIG. 17 shows a top plan view of a multilayer touch screen sensorelement 740 where the first and second patterned substrate have beenlaminated. Region 730 represented the overlap of the first and secondcontinuous regions. Region 732 represented the overlap of the firstcontinuous region and the second discontinuous region. Region 734represented the overlap of the second continuous region and the firstdiscontinuous region. And, region 736 represented the overlap betweenthe first and second discontinuous regions. While there was a pluralityof these overlap regions, for ease of illustration, only one region ofeach has been depicted in the figure.

The integrated circuits used to make mutual capacitance measurements ofthe transparent sensor element were PIC18F87J10 (Microchip Technology,Chandler, Ariz.), AD7142 (Analog Devices, Norwood, Mass.), andMM74HC154WM (Fairchild Semiconductor, South Portland, Me.). ThePIC18F87J10 was the microcontroller for the system. It controlled theselection of sensor bars which MM74HC154WM drives. It also configuredthe AD7142 to make the appropriate measurements. Use of the systemincluded setting a number of calibration values, as is known in the art.These calibration values can vary from touch screen to touch screen. Thesystem could drive 16 different bars and the AD7142 can measure 12different bars. The configuration of the AD7142 included selection ofthe number of channels to convert, how accurately or quickly to takemeasurements, if an offset in capacitance should be applied, and theconnections for the analog to digital converter. The measurement fromthe AD7142 was a 16 bit value representing the capacitance of the crosspoint between conductive bars in the matrix of the transparent sensorelement.

After the AD7142 completed its measurements it signaled themicrocontroller, via an interrupt, to tell it to collect the data. Themicrocontroller then collected the data over the SPI port. After thedata was received, the microcontroller incremented the MM74HC154WM tothe next drive line and cleared the interrupt in the AD7142 signaling itto take the next set of data. While the sampling from above wasconstantly running, the microcontroller was also sending the data to acomputer with monitor via a serial interface. This serial interfaceallowed a simple computer program, as are known to those of skill in theart, to render the raw data from the AD7142 and see how the values werechanging between a touch and no touch. The computer program rendereddifferent color across the display, depending on the value of the 16 bitvalue. When the 16 bit value was below a certain value, based on thecalibration, the display region was rendered white. Above thatthreshold, based on the calibration, the display region was renderedgreen. The data were sent asynchronously in the format of a 4 byteheader (0xAAAAAAAA), one byte channel (0x00-0x0F), 24 bytes of data(represents the capacitive measurements), and carriage return (0x0D).

Results of Testing of the System

The transparent sensor element was connected to the touch sensor drivedevice. When a finger touch was made to the glass surface, the computermonitor rendered the position of touch that was occurring within thetouch sensing region in the form of a color change (white to green) inthe corresponding location of the monitor. When two finger touches weremade simultaneously to the glass surface, the computer monitor renderedthe positions of touches that were occurring within the touch sensingregion in the form of a color change (white to green) in thecorresponding locations of the monitor. When three finger touches weremade simultaneously to the glass surface, the computer monitor renderedthe positions of touches that were occurring within the touch sensingregion in the form of a color change (white to green) in thecorresponding locations of the monitor.

Thus, embodiments of the METHODS OF PATTERNING A CONDUCTOR ON ASUBSTRATE are disclosed. One skilled in the art will appreciate that thepresent invention can be practiced with embodiments other than thosedisclosed. The disclosed embodiments are presented for purposes ofillustration and not limitation, and the present invention is limitedonly by the claims that follow.

1. A method of patterning a conductor on a substrate, comprising:providing an inked elastomeric stamp inked with self-assembledmonolayer-forming molecules and having a relief pattern with raisedfeatures, the relief pattern having a low density region measuring atleast 5 square millimeters comprising: an average area density value ofraised features between 0.5 to 10%; linear segments having a width valuebetween 0.5 to 25 micrometers; a distance value between adjacent raisedfeatures of less than 1 millimeter; contacting the raised features ofthe inked stamp to a metal-coated visible light transparent substrate;and etching the metal to form an electrically conductive micropatterncorresponding to the raised features of the inked stamp on the visiblelight transparent substrate.
 2. A method according to claim 1, whereinthe contacting step has a contact time in a range from 0.1 to 30seconds.
 3. A method according to claim 1, wherein the low densityregion has an average area density value of raised features between 1and 5%.
 4. A method according to claim 1, wherein a concentration ofself-assembled monolayer-forming molecules in the stamp adjacent to theprinting surface is between 0.05 and 20 millimolars and the contactingstep has a contact time in the range from 0.1 to 10 seconds.
 5. A methodaccording to 4, wherein the self-assembled monolayer forming moleculescomprise octadecylthiol.
 6. A method according to claim 1, wherein aconcentration of self-assembled monolayer-forming molecules in the stampadjacent to the printing surface is between 0.05 and 5 millimolars, thecontacting step has a contact time in the range from 0.1 to 10 seconds,and the self-assembled monolayer-forming molecules comprisehexadecanethiol.
 7. A method according to claim 1, wherein the lowdensity region has a uniform average area density value of raisedfeatures.
 8. A method according to claim 1, wherein the linear segmentshave a width value between 1 to 5 micrometers.
 9. A method according toclaim 1, wherein the maximum distance value between low density regionadjacent raised features is 500 micrometers.
 10. A method according toclaim 1, wherein all non-raised points in the relief pattern have amaximum separation distance from a raised linear feature of less than 1millimeter for all directions.
 11. A method according to claim 1,wherein all non-raised points in the relief pattern have a maximumseparation distance from a raised linear feature of less than 500micrometers for all directions.
 12. A method according to claim 1,wherein the stamp is inked with self-assembled monolayer-formingmolecules comprising a thiol, dialkyl disulfides, dialkyl sulfides,alkyl xanthates, dithiophosphates, and dialkylthiocarbamates.
 13. Amethod according to claim 1, wherein the low density region of theelectrically conductive micropattern comprises an electricallyconductive mesh micropattern.
 14. A method according to claim 1, furthercomprising electrically connecting the electrically conductivemicropattern to a touch sensor drive device.
 15. A method according toclaim 1, wherein the relief pattern comprises a raised feature measuringat least 50 micrometers in width.
 16. A method according to claim 15,wherein the monolayer-forming molecules comprise octadecylthiol, theconcentration of self-assembled monolayer-forming molecules in the stampadjacent to the printing surface is between 0.5 and 10 millimolars andthe contacting step has a contact time in the range from 0.5 to 5seconds.
 17. A method according to claim 15, wherein themonolayer-forming molecules comprise hexadecylthiol, the concentrationof self-assembled monolayer-forming molecules in the stamp adjacent tothe printing surface is between 0.5 and 1 millimolar and the contactingstep has a contact time in the range from 0.5 to 5 seconds.
 18. A methodof manufacturing a touch screen sensor, comprising: providing ametal-coated visible light transparent substrate having a relief patternwith raised features, the relief pattern having a low density regionmeasuring at least 5 square millimeters comprising: an average areadensity value of raised features between 0.5 to 10%; linear segmentshaving a width value between 0.5 to 25 micrometers; a distance valuebetween adjacent raised features of less than 1 millimeter; contactingan inked elastomeric stamp inked with self-assembled monolayer-formingmolecules to the metal-coated visible light transparent substrate; andetching the metal to form an electrically conductive micropattern on thevisible light transparent substrate raised features.
 19. A method ofpatterning conductors on a substrate, comprising: providing an inkedstamp with a relief pattern with raised features, the inked stampcomprising linear organosulfur self-assembled monolayer-formingmolecules with chain length from 16 to 18 atoms at a concentrationwithin the stamp of 1 to 10 millimolars, the relief pattern having a lowdensity region measuring at least 5 square millimeters comprising: anaverage area density value of raised features between 0.5 to 5%; linearsegments having a width value from approximately 1 to 4 micrometers; adistance value between adjacent linear segments of less than 500micrometers; a raised feature measuring at least 25 micrometers inwidth; contacting the inked stamp to a metal-coated visible lighttransparent substrate, the contacting step having a contact time in arange from 0.5 to 10 seconds, thereby depositing a pattern ofself-assembled monolayer; and etching the metal to form a transparentelectrically conductive micropattern corresponding to the raisedfeatures of the inked stamp on the visible light transparent substrate.20. A method according to claim 19, wherein the self-assembledmonolayer-forming molecules comprise octadecanethiol.